1. Field of the Invention
The present invention relates generally to a micro actuator having an electrostatically driven micro portion, and more particularly, to a micro actuator having a novel structure which includes clamping parts to enable the micro portion to be fixed at any position.
2. Description of the Related Art
A micro actuator comprises a stationary part and a displacement part which are disposed in close proximity to each other on a silicon substrate. A voltage is applied between the stationary part and the displacement part to generate an attractive force (electrostatic force) due to positive and negative static electricities occurring therebetween, thereby causing the displacement part to be displaced. As a result of formation of a minute displacement part on the silicon substrate by use of the IC fabrication process, the micro actuator as a micro machine is able to displace the displacement part in the form of a micro portion by a minute distance.
Such a micro machine is often called a micro electro/mechanical system (abbreviated as MEMS) in recent years, of which applications are proposed to various fields including a field requiring an especially precise positioning accuracy and including an apparatus such as a precision machine having a restricted accommodation space for a positioning mechanism.
The conventional micro actuator forms confronting faces of the stationary part and the displacement part which are spaced apart from each other by a minute distance, and a voltage is applied therebetween to cause a negative potential on one hand and a positive potential on the other, thereby generating an electrostatically attractive force (electrostatic force) to drive the displacement part. A variety of applications are presently conceived by making use of the drive of this displacement part.
The hitherto proposed micro actuator however merely displaces the displacement part by a predetermined distance. It may be effective for the example of application utilizing the minute distance displacement of the displacement part. However, there is a need to continue to apply the displacement voltage in order to positionally keep the displacement part.
Utilization for application has not substantially been effected so far, such as for example displacing the position of the displacement part by a predetermine distance and thereafter fixing it at that position.
It is therefore an object of the present invention to provide a novel structure of a micro actuator capable of keeping the position of the displacement part.
Another object of the present invention is to provide a micro actuator capable of displacing the displacement part to any direction and also keeping the position thereof.
In order to attain the above objects, according to an aspect of the present invention, there is provided a micro actuator displacing a micro portion by use of an electrostatic force, the micro actuator comprising a first stationary part; a displacement part spaced apart from the first stationary part by a predetermined distance in a confronting manner, the displacement part associated with the first stationary part by way of a first support, the displacement part being displaceable relative to the first stationary part; a second stationary part; and lock parts spaced apart from the second stationary part by a predetermined distance in a confronting manner, the lock parts associated with the second stationary part by way of a second support the lockparts being displaceable relative to the second stationary part; wherein the displacement part is displaced by application of a voltage between the first stationary part and the displacement part, the lock parts being displaced by application of a voltage between the second stationary part and the lock parts, and wherein the lock parts clamp the displacement part with no voltage applied, the lock parts releasing the displacement part with a voltage applied.
According to the above aspect, a second voltage is applied between the lock parts and the second stationary part to render the displacement part displaceable so that the position of the displacement part is displaced depending on a first voltage. Application of the second voltage is then halted to allow the lock parts to clamp the displacement part, after which application of the first voltage is halted. Therefore, the displacement part is displaced to a desired position where the displacement part can securely be fixed without subsequent application of any voltage.